1. Field of the Invention
The present invention broadly relates to clamping mechanisms, and more specifically, to toggle clamps that apply hold-down forces.
2. Description of Related Art
Toggle clamps have been used and known in the art for many years. A typical toggle clamp operates through a linkage system of levers and pivots to supply the clamping action and clamping force. The toggle action has an over-center lock point so the clamp cannot move or unlock unless the linkage is moved. All types of toggle clamps have the same toggle action, just oriented differently.
Toggle clamps are typically used to hold work pieces in place for processing and/or clamping two objects to one another, or for clamping an object to a work table or area. Toggle clamps generally are quickly engageable and disengageable with the work piece or object being held to provide a considerable holding or clamping force in order to hold the work piece or objects securely where needed.
The maximum clamping or exerting force developed by any toggle action clamp is attained when the three pivot points of the mechanism are in a straight line. However, this positioning of the pivot points makes no allowance for vibration and intermittent load conditions found in industrial applications, i.e., conditions which would unlock the clamp. Therefore, the typical positioning of the pivot points to produce the maximum holding force has one pivot point just past a plane established by the other two pivot points.
The typical mechanical advantage of a toggle clamp, that is, the correlation between the hold-down force in the clamped position and the force applied to the handle by a person, is on the order of 5 to 1. Accordingly, a force of 40 lbs. applied to handle (a person generally would be incapable of apply a greater force) would result in a hold-down force of 200 lbs. for a clamp with a 5 to 1 mechanical advantage. Any application needing a clamping force greater than approximately 200 lbs would require a pneumatically or hydraulically powered clamp which can apply a much greater initial force to the clamp than the average person. Many industrial applications require a clamping force greater than 200 lbs. thereby preventing the use of a simple, manually-operated toggle clamp.
Pneumatically or hydraulically powered clamps are complicated in design, relative to manually-operated clamps, causing manufacture and maintenance of these clamps to be an expensive proposition, particularly considering that each powered clamp needs a continuous source of power with the attendant design, manufacture and maintenance expenses. Conversely, a manually-operated clamp typically has a design that can be manufactured from an inexpensive stamping process and requiring no maintenance.
Consequently, there has been a longstanding need in the relevant art to produce a manually-operated toggle clamp that produces a clamped force in the range of pneumatically and hydraulically powered clamps.
Wherefore, it is an object of the present invention to provide a toggle clamp having a mechanical advantage greater than the typical manually-operated toggle clamp.
Another object of the present invention is to provide a manually-operated toggle clamp that produces a clamped force in the range of clamp forces produced by pneumatically powered clamps.
Still another object of the present invention is to provide a manually-operated toggle clamp that produces a clamped force in the range of clamp forces produced by hydraulically powered clamps.
Additional objects, advantages and novel features of the invention will be set forth in part in a description which follows, and in part will become apparent to those skilled in the art upon examination of the following specification, or may be learned by practice of the invention herein. The objects and the advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.